Electric motor.



EA'L'HNTED JAN. 21, 1908. L. A. TIRRILL.

ELECTRIC MOTOR.

APPLICATION FILED JUNE 7. 1906.

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UNITED STATES PATENT onnrion LEONARD A. TIRRILL, OF LYNN, MASSACHUSETTS,ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC MOTOR. I

Specification of Letters Patent.

Patented Jan. 21, 1908.

Application filed June 7, 1906- Serial No. 320.494.

To all whomit may concern:

Be it known that LLEONARD A. TIRRILL, a citizen of the United States,residing at Lynn, county of Essex, State of Massachusetts, have inventedcertain new and useful Improvements in Electric Motors, of which thefollowing is a specification.

The object of my present invention is to provide an electric motor witha power transmitting shaft coupled to the armature shaft of the motor bya speed changing mechanism.

In carrying out my invention '1' have made the power transmitting shaftand the speed changing mechanism a part of the motor structure and haveconstructed and arranged the parts in such a manner as to form a neatand effective mechanism particularly adapted for use in small portableunits such as breast drills and the like.

The various features of novelty which characterize my invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of my invention,however, reference maybe had to the accompanying drawings anddescriptive matter in. which I have'illustrated one of the.

forms'in which my invention may be embodied.

Of the drawings, Figure 1 is a sectional elevation of an electricallyactuated breast drill constructed in accordance with my invention; Fig.2 is a section on the line 2 2 of Fig. 1 Fig. 3 is a section on the line3 3 of Fig. 1,.Fig. 4 is an elevation of the split tension ring; andFig. 5 is a sectional elevation illustrating the means for securing oneend member in place.

Referringto the drawings, 1 represents the field ring of a motor whichin the form shown is made of a section of a steel tube. Diametricallyopposed pole pieces 2 are secured against the inner surfaces 'of thefield ring 1 by screws 3. Each pole piece is surrounded by a.winding orcoil 4 retained in place by a pole shoe .5 which in turn is secured tothe pole piece by a screw 6. As shown, the screws 3 and 6 for each poleextend into the ends of the same centrally formed passage in the polepiece.

Bonnets 7 and 8 are secured to opposite ends of the field ring 1.cured-to the field ring b means of screws 7 w 'ch are in turn sethreadedinto nuts 9 The bonnet 7 is secured to the .field ring by screw 10. Asupport 11 to be engaged by the operator is secured to the end of thebonnet 7 by a screw 12. As shown, a shield 13 surrounding the bonnet 7maybe held in place by the support 11. The bonnet 7 has secured to it abrush holder yoke 14 and is provided with a bearing 15 for one end ofthe armature shaft 16 of the motor. The opposite end of the armatureshaft 16 is reduced and enters the socket formed in the end of the powertransmitting shaft 17. The power transmitting shaft 17 is journaled intwo bearings 18 placed one at each end of a tubular portion 19 of thebonnet 8.

The bonnet 8 is provided with a shoulder 20 which abuts against the endof the field ring 1 and a reduced external threaded portion 21 which issecured into the adjacent internally threaded end of the field ring. Asshown, the bonnet 8 is provided with a tapared or conical surface 22'which is engaged y the outer-reversely tapered surface of a splittension ring 22. The inner surface of the split ring 22 iscylindricaland is engaged by three rollers 23 each in the form of a tubularcylinder of resilient material such as tempered steel. Each roller 23surrounds a roller member 24, the external diameter of which is slightlyless .than the internal diameter of the surrounding rollers. Each-rollermember 24 comprises an outer member 25 of suitable material such ashardened brass or bronze and aninner member 26 of softer metal such asthe so-called arguto metal. Themernbers 2.4 are journaled each on one ofthree steel studs 27 secured to the spider 28, which in turn issecuredtothe shaft 17. The shaft 16 has keyed upon it a sleeve 29 of suitablematerial such as steel against the periphery of which the rollers 23bear.

It will be observed that as the armature shaft 16 is rotated the rollers23 are rotated between the sleeve 29 and the inner surface of the splitring 22. The angular bodily movement of the rollers 23 about the axis ofthe shaft 16, causes a corresponding angular movement of the spider 28and shaft 17 In the construction shown the s eed of rotation of theshaft 17 will be direct y in proportion to but materially less than thespeed of rota- The resilient rollers 23 tion' of the shaft 16. are putunder a compression in a direction radial to the shaft 16 in a degreedependent upon the maximum load transmitted. To'

threaded portion 31 which engages the threads on the inner surface ofthe field ring.

Between the threaded portion 31 of the member 30 and the adjacent end ofthe split ring 22 extends-a reduced portion 32 of the member 30 havingformed in it a series of radial apertures 33. The field ring 1 isprovided with a suitable slot 34 through which may be inserted asuitable tool or bar-which enters the adjacent aperture 33 and serves asa means for rotating the member 30. As shown, the circumferentiallyextending slot 34 is longer than the space between the two holes 33. Theangular adjustment ofthe member 30 thus produced results, by reason ofthe threaded engagement of the field ring 1, in a corresponding axialmovement of the member 30. This regulates the extent to which the splitring 22 is forced into its conical seat in the bonnet member 8. By thisangular adjustment of the member 30 therefore the split ring 22 may becompressed more or less as desired.

The field ring may have secured to it a suitable operating switch orcircuit controlling device 35. It will be observed that the bearings 18are arranged so that the thrust of theshaft 17 is taken bythem and nottransmitted to the armature shaft. The shaft 17 may have secured to itintegrally or detachably, preferably the latter, any suitable tool to beoperated such as a drill, screw driver bit, etc. The constructionhereinbefore described has been found in practice to be highly desirablefor use insmall portable units such as breast drills or-the like whichare adapted to be held in engagement with the work by the hands of theoperator. 1

What I claim as new and desire to secure by Letters Patent of theUnitedStates, is,-

1. In an electric motor, a-field ring having a portion at one endinternally threaded, a bonnet or end member threaded exteriorly toengage the threaded portion of the field ring and formed with aninterior tapered surface,

anarmature shaft, a second shaft, a coupling for the shafts including asplit ring having an outer tapered surface engaging said inner taperedsurface, and means for moving said s 't ring axially comprising anannular member threaded exteriorly to engage the threaded portion of thefield ring.

2. In an electric motor, a field ring having a portion at one endinteriorly threaded, a bonnet or end member rovided with threadsengaging the threade portion of the field ring and formed with a taperedrecess, an

armature shaft, a second shaft in alinement therewith, a coupling forthe shafts comprising resilient rollers and a split ring surroundingthem and having an outer tapered surface entering said recess, and meansfor moving said split ring axially comprising an annular member havingthreads formed on its periphery to engage the threaded portion of thefield ring.

3. In an electric motor, a fieldring having a portion at one endthreaded interiorly, a

bonnet or end member provided with an exteriorly threaded ortion screwedinto the threaded portion 0 the field ring, said bonnet or end memberhaving a tapered recess formed in it, an armature shaft, asecond shaftin alinement therewith, and a coupling for the shafts including a splitring having an exterior tapered surface entering said recess, and meansfor moving said split ring axially in said recess to vary the diameterof the ring, comprising an annular member having a rib threadedexteriorly to engagethe threaded portion of the field ring and a secondportion engaging the end of the s lit ring, said second portion having acircun erentially extending series of holes formed in it, and the fieldring being provided with a slot or-opening to receive a tool enteringsaid holes to adjust said annular member angularly.

. In witness whereof, I have hereunto set my hand this 17 day of May,1906.

, LEONARD A. TIRRILL. Witnesses:

T. H. KENNEDY, FRANK. A. HUGO.

